Biology Notes Essay Research Paper DNA is

Biology Notes Essay, Research Paper

DNA is a very large polymer made up of many monomers called nucleotides

Each Dna nucleotide consist of:

a. the sugar deoxyribose

b. a nitrogen base

The only difference between the four types of Dna is there nitrogen bases.

The four nitrogen bases of DNA are the organic ring structures

a. adenine

b. thymine

c. guanine

d. cytosine

One way to determine the structure of a substance is by X-ray diffraction.

X-ray diffraction—-a beam is passed through a pure crystal of the substance.

Rosalind Franklin carried out x-ray diffraction on very pure fibers of DNA.

The patterns on her x-ray film showed that the phosphate of one nucleotide was linked

to the sugar of the next, forming a continuos chain.

The phosphate-sugar chain forms a backbone for each strand. The nitrogen bases of

each strand pair with the nitrogen bases of the other strand by hydrogen bonding.

The nitrogen base Adenine (A), only bonds with Thymine (T), and the base Guanine

(G), only bonds with Cytosine (C).

Because there are two strands in a spiral, the shape of DNA is described as a double

helix.

The DNA double helix is compared to a twisted ladder. The sides of the ladder are the

sugar-phosphate backbones and the rungs are the pairs of nitrogen bases.

Replication—- The process by which a DNA molecule is copied.

The four nitrogen base ?A?, ?C?, ?G?, and ?T? make up the genetic alphabet.

Each strand then serves as a pattern along which a new strand can form.

When a DNA molecule replicates enzymes ?unzip? the two strands along the paired

bases

Codon—–as sequence of three bases.

a codon is a unit of the genetic code.

different codons specify different amino acids.

There are 64 different combinations possible with the four different nitrogen bases

taken three at a time.

There are only 20 amino acids. Therefore, three or four codons may stand for the

same amino acid.

One codon is a start codon that begins the production of a protein chain.

Three different codons are stop codons which end the protein chain.

The genetic code is copied for use at the site of protein synthesis, the ribosome.

Like DNA, RNA is a nucleic acid made of bonded nucleotides.

DNA contains the sugar deoxyribose but RNA contains ribose a different sugar.

Instead of the base Thymine RNA contains the base Uracil (U)

Uracil bonds with the adenine just like thymine.

There are three kinds of RNA:

a. messenger RNA (mRNA)

b. transfer RNA (tRNA)

c. ribosomal RNA (rRNA)

mRNA is the RNA copy of the DNA code for the sequence of amino acids in a